The proper fitting of contact lenses involves various ophthalmic measurements, such as iris diameter, pupil diameter, height of the palpebral fissure, as well as parameters of the contact lens. Unfortunately, present day instruments and methods used for making such measurements are generally inefficient, cumbersome, or unduly expensive.
Measurements of the pupil, iris and fissure are currently made with the use of a hand held graduated rule or a reticle used with a simple magnifier or a more sophistocated slit lamp. The use of the rule is subject to the accuracy of the markings on the rule, elimination of eye movement during measuring, elimination of parallax errors and unwanted shadows. Even the most sophistocated systems, however, have an accuracy of about .+-.0.3 mm, whereas proper fitting of some types of contact lenses require accuracy within .+-.0.1mm.
None of the above instruments are used to measure the parameters of contact lenses, such as overall diameter, optical zone, and peripheral curve. Instead, a separate instrument is employed and usually comprises a 7.times.magnifier having a reticle with scale markings. Proper use of the instrument requires exact positioning of the lens relative to the scale, which is often a cumbersome procedure.
In summary, there is presently no instrument capable of making highly accurate and reliable measurements of the eye, and no single instrument capable of making measurements of both the eye and the contact lens.